The present invention relates to photoelectric keyboard switches for a computer.
U.S. Pat. No. 5,136,156 to Nounen et al. discloses a photoelectric switching device, which comprises a four-sided frame, three pairs of arrays of light-emitting elements, photo-detecting elements, and a control means. Each array of the light-emitting elements is mounted on a side of the frame. Each of the photo-detecting elements is mounted on an opposite side of the frame from which the light-emitting elements are mounted.
Three pairs of the arrays of the light-emitting elements and photo-detecting elements together provide a matrix of regions inside the frame. When the light paths between the light-emitting elements and the photo-detecting elements are blocked by a stylus, such as a finger, sensed, blocked signals are transmitted to a control means, such as a computer, which discriminates the coordinates of the stylus on the switch device, and displays a pattern having several regions allocated for control of optional equipment.
The Nounen device does not provide a convenient flexibility for a thumb to operate the device, together with other fingers. Generally speaking, joint operation of a thumb and other four fingers of a hand is needed for regular typing operations. The device disclosed herein provides improved means for a thumb to work together with the other four fingers of a hand, to do typing.